An exception of type Microsoft.SharePoint.PostSetupConfiguration.PostSetupConfigurationTaskException was thrown

Failed to upgrade SharePoint Products.
This is a critical task. You have to fix the failures before you can continue. Follow this link for more information about how to troubleshoot upgrade failures: http://go.microsoft.com/fwlink/?LinkId=259653

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An exception of type Microsoft.SharePoint.PostSetupConfiguration.PostSetupConfigurationTaskException was thrown. Additional exception information:
Upgrade [SPContentDatabase Name=SP_Content_XXX] failed. (EventID:an59t)

Exception: The upgraded database schema doesn't match the TargetSchema (EventID:an59t)

(EventID:an59t)

Upgrade Timer job is exiting due to exception: Microsoft.SharePoint.Upgrade.SPUpgradeException: The upgraded database schema doesn't match the TargetSchema

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To diagnose the problem, review the application event log and the configuration log file located at:X:\...\logs\trace\PSCDiagnostics_11_19_2020_19_28_44_400_325989182.log

Upgrade-SPContentDatabase SP_Content_XXX -NoB2BSiteUpgrade

Get-SPContentDatabase | ?{$_.NeedsUpgrade -eq $true} | Upgrade-SPContentDatabase -NoB2BSiteUpgrade